I. Field of the Invention
The present invention relates to a plasma display panel. In particular, the present invention relates to a plasma display panel characterized by a carbon concentration of a dielectric layer thereof. The present invention also relates to a method for producing such a plasma display panel.
II. Description of Related Art
The market for large screen flat-panel displays has been recently growing. In these circumstances, a plasma display panel suited to high-definition pictures and a large screen has been further developed.
The plasma display panel comprises a front panel and a rear panel opposed to each other. The front panel and the rear panel are sealed along their peripheries. Between the front panel and the rear panel, there is formed a discharge space filled with a discharge gas (helium, neon or the like).
The front panel is generally provided with a glass substrate, display electrodes (each of which comprises a scan electrode and a sustain electrode), a dielectric layer and a protective layer. Specifically, (i) on one of principal surfaces of the glass substrate, the display electrodes are formed in a form of stripes; (ii) the dielectric layer is formed on the principal surface of the glass substrate so as to cover the display electrodes; and (iii) the protective layer is formed on the dielectric layer so as to protect the dielectric layer.
The rear panel is generally provided with a glass substrate, address electrodes, a dielectric layer, partition walls and phosphor layers (i.e. red, green and blue fluorescent layers). Specifically, (i) on one of principal surfaces of the glass substrate, the address electrodes are formed in a form of stripes; (ii) the dielectric layer is formed on the principal surface of the glass substrate so as to cover the address electrodes; (iii) a plurality of partition walls are formed on the dielectric layer at equal intervals; and (iv) the phosphor layers are formed on the dielectric layer such that each of them is located between the adjacent partition walls.
In operation of the plasma display panel, ultraviolet rays are generated in the discharge space upon applying a voltage, and thereby the phosphor layers capable of emitting different visible lights are excited. As a result, the excited phosphor layers respectively emit lights in red, green and blue colors, which will lead to an achievement of a full-color display.
The dielectric layers can serve as a capacitor. Especially as for the dielectric layer of the front panel, not only a high performance of capacitor is required for achieving a high efficiency of the discharge, but also a resistance to a dielectric breakdown phenomenon is required (such breakdown phenomenon may occur when the voltage is applied on the dielectric layer). See Japanese Patent Kohyo Publication No. 2003-518318 and Japanese Patent Kokai Publication No. 11-195382, for example.
Especially in recent years, there has been an increasing demand for a higher definition and a lower power consumption of the plasma display panels. Thus, some research has been done in order to increase not only the energy effectiveness of the discharge gas but also the number of scanning lines. The realization of a higher definition leads to a smaller pitch between the electrodes, and thereby the dielectric breakdown may occur between the electrode and the dielectric layer upon applying the voltage. For this reason, it is required that the dielectric layer has a lesser physical defect, such as peeling or cracking therein or on its surface.
Moreover, the smaller the panel opening area becomes, the lower the panel brightness becomes. Thus, the dielectric layer is required to have a high purity and a low dielectric constant (or low permittivity). To this end, it is necessary to prevent the dielectric layer from turning yellow. This yellow discoloration of the dielectric layer is known as “yellowing” or “yellowing phenomenon” wherein the dielectric layer is deteriorated to turn yellowish due to a secondary reaction with the electrodes upon calcining the dielectric layer.
Therefore, an object of the present invention is to provide a plasma display panel characterized by a dielectric layer substantially free from the cracking, the yellowing and the like.